1. Field
The present invention relates to internal combustion engines. In particular, engines having pooled oil and which rely, at least in part, on internal lubrication at least in part
2. Description of the Related Art
An internal combustion engine having the following structure is known from Japanese Patent Publication No. 2007-291950 (Japan '950). Specifically, in the internal combustion engine, a cam chain chamber which houses a drive sprocket and a part of a cam chain wound around the drive sprocket, is formed between a crankcase and a cover which is connected to the crankcase and covers a side of the crankcase. The cam chain chamber is formed also to be capable of pooling oil in a lower portion thereof. In addition, a balancer is housed in the cam chain chamber and arranged at a position where the balancer is capable of splashing the oil pooled in the lower portion inside the cam chain chamber.
Meanwhile, the oil pooled in the lower portion of the cam chain chamber is sucked in by an oil pump, and then is supplied from the oil pump to a lubricating portion of the internal combustion engine. When oil splashed by the rotation of the balancer falls down on an oil sump, bubbles are generated in the oil in the oil sump. As a result, air is likely to be mixed into the oil which is to be sucked by the oil pump.